Pre-prosesor with SASS, using flexbox and grid for the page

There're a lot of diffucult things while building this project, I have noone to ask for, and every error, I can't find it on google because me by myself didn't know cause of the error. I am solo fighter who just knowing html existence about one and a half ago. The are that make me unsure is the mockups area, that's very confusing me.